1. Field of the Invention
The present invention relates to optical pulse characterization.
2. Description of the Related Art
Accurate characterization of an optical pulse, including the determination of its optical phase, is a nontrivial task in part because conventional photodetectors are not sensitive to the optical phase. At the same time, accurate determination of the optical phase is required to ensure proper encoding/decoding of various multi-level phase modulation formats, e.g., phase-shift keying (PSK) and quadrature-amplitude modulation (QAM). Several techniques have been demonstrated to be suitable for the characterization of the optical phase of relatively short optical pulses. Representative examples of such techniques can be found, e.g., in commonly owned U.S. Pat. Nos. 7,006,230, 6,885,490, and 6,856,927, all of which are incorporated herein by reference in their entirety. However, one problem with these techniques is that each of them is rather technically involved. For example, one of the techniques disclosed in U.S. Pat. No. 6,856,927 can determine an optical phase profile for a pulse train based on acquisition and processing of 32 different spectra.